The invention relates, according to a first aspect, to a method for the bordering of decorative material, in particular a carpet, a fabric or a sheet, in which a one-piece border is formed in a die mould for back-pressing and/or back-injection, at least on parts of an edge of this decorative material, the said border comprising a rim which extends essentially at right angles to the main direction of extent and along the edge of this decorative material and which comprises a multiplicity of fingers which engage over the decorative material, the production of the rim and of the fingers and their connection to the decorative material taking place in one operation.
According to a second aspect, the invention relates to a die for producing a rim and fingers of a one-piece plastic border of decorative materials, the said border being capable of being produced by means of an back-pressing method or a combined back-pressing/back-injection method and, in particular, being capable of being integrally formed onto a decorative layer or of being connected to the latter.
Decorative materials, such as overlay or lining carpets for motor vehicles, are conventionally beaded. This beading is generally not detrimental to the desired flexibility of the carpet edge (adaptation to prevailing unevenesses). However, such beadings are costly to produce and, moreover, have a considerable tendency to become soiled. The lifetime of such an overlay carpet is usually limited precisely because a beading has been damaged. In view of this problem, overlay carpets for motor vehicles are produced, for example, by first producing a hard-wearing carrier material from plastic by means of the injection-moulding technique. A decorative material, that is to say a carpet cut to size, has to be glued into this carrier material in a further operation. So that cutting tolerances in the carpet can be absorbed or coloured, but also to make a reinforced border available for the carpet edge, the carrier material is preferably produced with an undercut. This undercut, on the one hand, solves the problem of the cutting tolerances, but, on the other hand, there is a new problem: complicated, that is to say costly, injection moulds with corresponding slide systems are necessary in order to produce a clean undercut with an overhang which is suitable for covering tolerances of a plurality of millimetres. Only with the aid of such slide systems is it at all possible to remove the ready-moulded carrier material for the mould without any damage. Moreover, carpet edges bordered in this way prove to be insufficiently flexible. Furthermore, in practice, the operation of gluing the decorative material onto the carrier material represents an additional increase in price of the final product.
In many fields of technology, structural parts made of plastic are used, which have to satisfy not only functional requirements, but also aesthetic demands. One example of this, among many, is motor vehicle manufacture, where such plastic structural parts are used for interior trims, rear-window shelves, boot covers, dashboards and the like. To give these an aesthetically attractive design, therefore, a decorative layer is often attached as a separate surface layer to a visible side of the plastic structural part. For reasons of easy disposal or simplified reuse, the decorative material should preferably be produced from the same material as the plastic structural part carrying it. Such monomaterials can thus be recycled substantially more cost-effectively than composite materials which first have to be separated. The so-called back-pressing method was developed in order to produce plastic structural parts of this kind. This method is described in the publication xe2x80x9cKunststoffe im Automobilbau, VDI-Verlag GmbH, Dusseldorf 1994xe2x80x9d [xe2x80x9cPlastics in Motor Vehicle Manufacture, VDI-Verlag GmbH, Dusseldorf 1994xe2x80x9d]. It provides for fastening a decorative layer to a die upper part of an opened die mould in such a way that it covers the surface of the die upper part, if appropriate over the entire area. Subsequently, a melted and therefore flowable plastic mass is injected or inserted into the die mould which continues to remain open. Thereafter, the mould is closed, with the result that the plastic mass is distributed uniformly in the mould under the closing pressure and, at least in the case of decorative materials with pores, such as, for example, textile materials, penetrates partially into the decorative material. The plastic mass subsequently solidifies and makes an intimate bond with the decorative layer. This back-pressing method may also be combined with the back-injection method.
Such an back-pressing and/or back-injection method may be used in order to produce a carrier layer which is suitable for a decorative material. As a result of the one-piece production of this carrier layer, which could be integrally formed onto an edge, the cutting tolerances in the carpet would be compensated and production simplified by the avoidance of the operation of gluing on the carpet. A serious problem here, however, is the positioning of the edge of the decorative material in the cavity of a die mould for back-pressing or back-injection. As a result of the positive-displacement pressing of the plastic material melt introduced, the edge of the decorative material may, for example, be upset or raised in an unforseeable way. It is therefore not possible to ensure a clean formation of a border which reliably covers the edge of the decorative material. Moreover, the edge can scarcely achieve the desired flexibility in this way.
Devices and methods known from the prior art disclose means for reinforcing the decorative material/carrier layer connection, but they do not propose any means for designing a more flexible border of the edge of a decorative material:
U.S. Pat. No. 4,491,556 discloses a method and a device for producing a carpet mat, with an injection-moulding unit which comprises two moulds. A multiplicity of pits is arranged in a first mould which has a depression for receiving a carpet running parallel to the parting plane. These pits correspond to intervals arranged in that part of a second mould which corresponds to the depression of the carpet receptacle. At the same time, at least one of the moulds has a cavity for forming the edges of a mat underlay, and the method involves fitting a carpet into this receiving depression and injecting a thermoplastic resin into the space between the carpet and the pits, in order to provide a mat underlay which is simultaneously connected to the carpet. This publication relates mainly to underlaying the carpet material with a plastic bed (cf. FIGS. 6 and 7).
DE 37 12 882 relates to a lining moulding, in particular a floor covering of a motor vehicle, the said moulding having a bordered carpet layer and additional layer. The border is formed by a solid-profile plastic body. This is integrally formed directly onto the edges of the carpet layer and additional layer. In the region of the edge of the carpet layer, the pile of the latter is embedded into the plastic body.
CA 960 827 relates to a method for producing a utensil (in particular, a perforated lid for covering a frying pan when meat is being fried) which comprises a metal grid and a cast plastic ring. Here, the plastic ring consists of a thermoplastic material and surrounds the edge of the grid. The method involves the following steps: production of a metal grid having at least one marking hole; provision of a two-part casting mould comprising a cavity, by means of which an outer ring can be cast, which is formed in such a way that the metal grid is bordered and supported; provision of at least one pin in one moulding, the said pin in each case fitting a marking hole of the grid; provision of a depression in the other moulding, the pin fitting into the said depression when the two mouldings are joined together; orientation of the metal grid with all the marking holes and pins arranged therein; closing of the mould and execution of the injection-moulding operation. For the purpose of improving the stability, the metal grid/ring connection is to be reinforced.
GB 1 271 860 relates to the production of filter elements consisting of a filtering membrane, the outer edge of which is embedded in a sealing element. For the better retention of the membrane during injection-moulding, the two mould halves have lugs which are always located opposite lugs arranged on the other mould half, so that a membrane laid between the mould halves is held securely by means of the pairs of lugs, even when injection is carried out at high pressure. A holding ring is cast on the lugs on the inside. This holding ring is connected via some webs to the outer ring which acts as a sealing element.
The object of the invention is to supply borders of decorative materials, in particular carpets, textiles or sheets, with a border which is integrally formed by the back-pressing and/or back-injection of a flowable mass and which cleanly borders and reinforces at least parts of the edge of these decorative materials and affords improved flexibility, as compared with the prior art, and which during the production of which the use of slides for producing an undercut may be dispensed with.
According to a first aspect of the invention, this object is achieved in that a method of the type described in the introduction, for the bordering of decorative material, in particular a carpet, a fabric or a sheet, is proposed, in which a border is formed in a die mould for back-pressing and/or back-injection, at least on parts of an edge of this decorative material, and which is characterized by the following steps:
insertion of decorative material into a cavity of the die mould, the said cavity being formed by die halves;
introduction of a flowable mass into the cavity of the die mould;
closing of the die mould;
distribution of the flowable mass in the cavity;
one-piece formation of a rim, which extends essentially at right angles to the main direction of extent of the decorative material and along the edge of this decorative material, and of a multiplicity of fingers which engage over the decorative material;
connection of the rim and of the fingers to the decorative material;
ejection of the bordered decorative material after the at least partial solidification of the mass.
A plastic melt is preferred as a flowable or pasty mass when this method is carried out.
Moreover, with a device of the type described in the introduction being proposed, the object is achieved, according to the invention, in that this device for the bordering of decorative material, in particular a carpet, a fabric or a sheet, comprises a die mould for back-pressing and/or back-injection, by means of which a border can be formed at least on parts of the edge of this decorative material, the device being characterized in that this die mould has recesses which are designed for the moulding of fingers and, consequently, for the flow-round of a mass and bordering the edge of the decorative material, and in that this die mould has holding webs, by which the recesses can be separated from one another by means of which the decorative material can be positioned, in order to prevent deformations of the edge, these holding webs reaching as far as the recess for a rim which extends essentially at right angles to the main direction of extent and along the edge of this decorative material and which can be produced in one piece with a multiplicity of fingers engaging over and/or under the decorative material and can be connected to the decorative material in the same operation.
Special embodiments of the method according to the invention and of the device according to the invention are found in the subclaims, which also list production means or mould parts, such as depressions, webs and the like, for the integral forming of webs, supporting lattices, supporting plates, bosses, strips, orifices and the like, and for the bordering of the same or different decorative materials or for producing an insert on one side or on both sides of a rim which, if appropriate, is narrowed on one side or on two sides.
The method described above is basically suitable for all plastics and other flowable or pasty masses which can solidify and which can be processed by means of the back-pressing method or by back-injection. Those materials may be used as a surface layer or decorative layer which make a firm connection with such a mass or with such a plastic during the back-pressing operation. Textile materials, such as carpets and knitted fabrics, as well as plastic sheets, may be mentioned, merely by way of example, in this respect. However, those combinations of masses or plastics and materials of the decorative layer which are of purely the same sort are preferred, so that the bordered decorative material, after its intended use, can be comminuted at little outlay and reused as monomaterial.
The fingers integrally formed according to the invention onto the rim are obtained by means of corresponding recesses in one or both die-mould halves. Holding webs of the die mould extend between these recesses as far as the rim, that is to say up to and beyond the edge of the inserted decorative materials, and rest directly against the decorative material. This ensures, during the positive-displacement pressing or during the back-injection of the flowable mass or plastic material melt, that the latter can flow round the decorative material, so as to form the rim and the fingers, but that the decorative material is held reliably at its edge and is positioned in the cavity of the die mould. Deformations, such as, for example, upsetting or raising the decorative material above the level of the main direction of extent, are thereby avoided. The use of slides may be dispensed with as a result of the inventive design of the die mould.
The dimensions of the fingers are preferably determined in such a way that the latter are substantially longer than they are wide. The distances between the fingers are, at the same time, selected in such a way that, depending on the stability or deformability of the decorative material, this decorative material cannot reach the upper level of the fingers or the rim, by being bent up or deformed, either during back-injection and/or back-pressing or in the finished product. Such a rim integrally form in one piece onto the decorative material has a highly subdivided longitudinal structure, with the result that good flexibility of the border is achieved.
In preferred variants of the method, fingers can be provided on the top side and the underside of the rim. Moreover, if the decorative material has sufficient stability (if, for example, it is a hard-wearing carpet), the height of the rim may be reduced to the thickness of the carpet; the integrally formed fingers then engage over and under the carpet. Optionally, in this case, the upper fingers are designed in such a way that the carpet pile, which straightens up again after back-pressing and/or back-injection, does not reach, or only just reaches, or does not project above, the upper level of the fingers or of the rim. Furthermore, these fingers may merge into ribs integrally formed on the rim or the ribs integrally formed on the outside of the rim may be continued in the fingers. The advantage of this is that the rim may be designed to be even thinner and, nevertheless, the edge of the decorative material is reliably reinforced and bordered.
In preferred embodiments of the invention, there may be provision for the two mould halves to be capable of being closed and opened in a straight movement. This makes it possible to reduce the production time for the border of a decorative material appreciably.